Magnetic microplate assembly

ABSTRACT

Magnetic microplate assemblies are disclosed for assaying of biological activated magnetic particles from a supernatant. The assemblies include a magnetic microplate holder and a microplate including a plurality of wells for retaining the magnetic particles. The microplate holder includes a plurality of magnets for attracting the magnetic particles to the wells and a plurality of detents for securing the microplate in the holder. The detents allow the microplate to be tightly retained in the holder when the assembly is turned over to discard supernatant and wash buffer applied to rinse supernatant from the magnetic particles.

RELATED APPLICATIONS

This application claims priority to U.S. provisional application61/131,272, filed on Jun. 9, 2008, the entire contents of which areincorporated by reference.

BACKGROUND

This disclosure relates to an improved magnetic microplate assembly forbiological agent separation and purification.

The use of biological activated magnetic particles or beads as carriersfor biological agent separation and purification is well known. Severalhand-held magnetic microplate assemblies are commercially available forseparating biological activated magnetic beads from a supernatant andassaying the beads. Such separators may include a magnet base and amicroplate having a plurality of wells (typically six, twelve,twenty-four, forty-eight or ninety-six wells) for retaining biologicalactivated magnetic beads attracted by the base. In order to assaybiological activated magnetic beads, the beads are delivered to thewells in a supernatant, and the beads are attracted to and retained inthe wells by the magnet base. The supernatant is separated from thebeads and discarded by inverting the microplate such that the uppersurface of the microplate generally faces downward. A wash buffer maythereafter be applied to wash the beads in the wells, and the washbuffer may be discarded by inverting the microplate.

During the process of inverting the microplate to discard thesupernatant and the wash buffer, the microplate and the magnet base mustbe held together in order to prevent the loss of any magnetic beads fromthe wells. In some known magnetic microplate assemblies, the magnet baseand the microplate are held together with one or more rubber bands thatare wrapped around the magnet base and the microplate. Because therubber bands tend to trap supernatant and wash buffer and tend to shifttheir positions during the washing step, the rubber bands can causecross-contamination of assays.

It is therefore desirable to provide a magnetic microplate assembly thatincludes improved means for securing the microplate during inversion ofthe assembly for discarding supernatant and wash buffer.

SUMMARY

Magnetic microplate assemblies are disclosed for separating biologicalactivated magnetic particles from a supernatant. The assemblies includea magnetic microplate holder and a microplate including a plurality ofwells for retaining the magnetic particles. The microplate holderincludes a plurality of magnets for attracting the magnetic particles tothe wells and a plurality of detents for securing the microplate in theholder. The detents allow the microplate to be tightly retained in theholder when the assembly is turned over to discard supernatant and washbuffer applied to rinse supernatant from the magnetic particles.

According to one embodiment, the detents of the microplate holdercomprise a plurality of catches or rib members disposed on end walls ofthe microplate holder and positioned to engage a flange of themicroplate to secure the microplate in the microphage holder.

According to another embodiment, the detents of the microplate holdercomprise a plurality of resilient detents disposed in end walls of themicroplate holder and a plurality of dowel pins disposed near one of theend walls, wherein the resilient detents and dowel pins are positionedto engage a flange of the microplate to secure the microplate in themicroplate holder.

Methods of loading a microplate in a microplate holder and unloading amicroplate from a microplate holder are also disclosed.

Further features and advantages of the invention will be apparent uponreference to the following description, appended drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a magnetic microplate assembly includinga microplate and a magnetic microplate holder according to oneembodiment;

FIG. 2 is another perspective view of the microplate assembly of FIG. 1;

FIG. 3 is a perspective view of the microplate holder of FIGS. 1 and 2;

FIG. 4 is another perspective view of the microplate holder of FIGS. 1and 2;

FIG. 5 is a side cross-sectional view taken along line A-A of FIG. 1;

FIG. 6 is a side cross-sectional view illustrating methods of loadingthe microplate in the microplate holder and unloading the microplatefrom the microplate holder in the embodiment of FIGS. 1-5;

FIG. 7 is a perspective view of a magnetic microplate assembly includinga microplate and a magnetic microplate holder according to anotherembodiment;

FIG. 8 is another perspective view of the microplate assembly of FIG. 7;

FIG. 9 is a perspective view of the microplate holder of FIGS. 7 and 8;

FIG. 10 is another perspective view of the microplate holder of FIGS. 7and 8;

FIG. 11 is a side cross-sectional view taken along line B-B of FIG. 7;

FIG. 12 is a side cross-sectional view illustrating a method of loadingthe microplate in the microplate holder and unloading the microplatefrom the microplate holder in the embodiment of FIGS. 7-11; and

FIGS. 13 and 14 show spring-and-ball plungers employed in the embodimentof FIGS. 7-12.

FIG. 15 is an exploded view of the magnetic microplate assembly.

DETAILED DESCRIPTION

FIGS. 1-6 illustrate a magnetic microplate assembly 10 according to afirst embodiment. Referring to FIGS. 1-5, the assembly 10 includes amagnetic microplate holder 20 and a microplate 50 retained in the holder20. The assembly 10 is configured to separate biological activatedmagnetic particles or beads (not shown) from a supernatant (not shown)to enable assaying of the particles or the supernatant.

The microplate 50 is formed from a single member which has an upperplatform 52, a perimeter wall 54 extending downward from the upperplatform 52, and multiple wells 58 integrally formed in the upperplatform 52 for holding liquid samples. The perimeter wall 54 includesan upper wall portion 55 and a stepped-out bottom flange 57 including ahorizontal ledge or lip 56 joined to the upper wall portion 55. Asshown, the wells 58 in the microplate 50 are arranged in aneight-by-twelve array, thereby forming a ninety-six well plate. However,it should be understood that any other number of wells, such as six,twelve, twenty-four, forty-eight, three hundred eighty-four or fifteenhundred thirty-six or any other number may be provided, and variousarray designs may be employed. The microplate 50 may be constructed ofnon-magnetic plastic or other suitable materials.

Turning to FIGS. 3 and 4, the microplate holder 20 includes a bottomwall 22, a first end wall 24 formed at a first end of the bottom wall22, and a second end wall 26 formed at a second end of the bottom wall22, and substantially open side sections 28. The holder 20 is may beconstructed of non-magnetic plastic, however, other materials may beused. A plurality of cylindrical magnets 30 are positioned in the bottomwall 22. In the embodiment shown, the microplate holder includesninety-six magnets 30 arranged in an eight-by-twelve array, with eachmagnet 30 being positioned for alignment directly below a well 58 of themicroplate 50. However, it should be understood that other numbers andarrangements of magnets are possible. For example, embodiments may beemployed in which there are fewer magnets 30 than wells 58, and eachmagnet 30 is positioned for alignment with a group of multiple wells 58.Additionally, the number of magnets 30 employed may vary based on thenumber of wells 58 provided in the microplate 50.

Referring still to FIGS. 3 and 4, the end wall 26 includes a cut-outportion 27 which allows a user to grab an end portion of the microplate50 during loading of the microplate 50 into the microplate holder 20, aswell as during unloading of the microplate 50 from the microplate holder20. The substantially open side sections 28 allow a user to grab sideportions of the microplate 50 and also serve to prevent liquidaccumulation in the assembly 10 during washing of the microplate 50. Theend walls 24, 26 are flexible and resilient in the longitudinaldirection L, to allow loading of the microplate 50 into the holder 20and unloading of the microplate 50 from the holder 20, as is describedin detail in following paragraphs.

As shown in FIGS. 3-6, the microplate holder 20 includes a plurality ofdetents or catches 32, 34 protruding from the interior surfaces 24 a, 26a of the end walls 26 for engaging the microplate 50 and retaining themicroplate 50 in the microplate holder 20. The catches 32, 34 may be ribmembers or other elements suitable for engaging and retaining themicroplate 50. The catches 32, 34 may be located at a height above thebottom wall 22 that allows the bottom flange 57 of the microplate 50 tobe tightly secured below the catches 32, 34, as will be described ingreater detail in following paragraphs. Referring to FIGS. 1-4, a singlecatch 32 is provided at a laterally central area of the end wall 24, andtwo catches 34 are provided near opposite lateral ends of the end wall26. However, it should be understood that the number and location of thecatches 32, 34 can vary as desired.

FIGS. 1, 2 and 5 show the microplate assembly 10 in a fully assembledconfiguration, wherein the microplate 50 is secured in the holder 20. Inthe assembled configuration, the bottom flange 57 of the perimeter wall54 is retained under the catches 32, 34 at ends 50 a, 50 b of themicroplate 50. More specifically, the ledge 56 is positioned under andengages the undersides of the catches 32, 34 at ends 50 a, 50 b, therebypreventing vertical movement of the microplate 50 during use. In orderto separate biological activated magnetic particles from a supernatant,the supernatant is delivered into the wells 58, and the particles areretained in the wells 58 under the force of magnetic fields generated bythe magnets 30. The supernatant can be discarded by inverting or tiltingthe assembly 10 such that the upper platform 52 of the microplate 50 isturned downward. A wash buffer (not shown) may thereafter be applied tothe microplate 50 to wash residual supernatant away from the upperplatform 52 and the particles in the wells 58. The wash buffer may thenbe discarded by inverting or tilting the assembly 10. Due to the catches32, 34 preventing vertical movement of the microplate 50 within theholder 20, the microplate 50 is securely retained close to the magnets30 within the holder 20 during inversion or tilting of the assembly 10,thereby allowing the particles to remain within the wells 58.

FIG. 6 illustrates how the microplate 50 can be loaded into the holder20. As shown in FIG. 6, the microplate 50 can be loaded into the holder20 by: tilting the end 50 b of the microplate 50 slightly downward inthe direction D1; sliding the microplate 50 longitudinally forward inthe direction L1 such that the flange 57 is positioned under the catches34 at the end 50 b and the ledge 56 engages the undersides of thecatches 34 at the end 50 b; pressing the end 50 b against the end wall26 so as to flex the end wall 26 outward in the direction L1 from itsnatural position and thereby allowing the end 50 a to movelongitudinally in the direction L1 inside of the catch 32; pressing theend 50 a down in the direction D1 such that the flange 57 travelsdownward past the catch 32 at the end 50 a; and then releasing themicroplate 50 such that the end wall 26 returns to its natural positionand forces the microplate 50 to slide longitudinally backward in thedirection L2 such that the flange 37 is positioned under the catch 32 atthe end 50 a and the ledge 56 engages the underside of the catch 32 atthe end 50 a.

Alternatively, the microplate 50 can be loaded into the holder 20 byfirst inserting the end 50 a. Specifically, the microplate 50 can beloaded into the holder 20 by: tilting the end 50 a slightly downward inthe direction D1; sliding the microplate 50 backwards in the directionL2 such that the flange 57 is positioned under the catch 32 at the end50 a and the ledge 56 engages the underside of the catch 32 at the end50 a; pressing the end 50 a against the end wall 24 so as to flex theend wall 24 outward in the direction L2 from its natural position andthereby allowing the end 50 b to move longitudinally in the direction L2inside of the catches 34; pressing the end 50 b down such that theflange 57 travels downward past the catches 34 at the end 50 b; and thenreleasing the microplate 50 such that the end wall 24 returns to itsnatural position and forces the microplate 50 to slide longitudinallyforward in the direction L1 such that the flange 37 is positioned underthe catches 34 at the end 50 b and the ledge 56 engages the undersidesof catches 34 at the end 50 b.

Still referencing FIG. 6, the microplate 50 can be unloaded from theholder 20 by: flexing the end wall 26 outward in the direction L1 and/orpushing the microplate 50 in the direction L2 so as to flex the end wall24 outward in the direction L2, such that the flange 57 is movedlongitudinally inside of the catches 34 in the direction L2 at the end50 b; lifting the end 50 b up in the direction D2 such that the flange57 moves up past the catches 34 at the end 50 b; sliding the microplate50 forward in the direction L1 such that the flange 57 is moved past thecatch 32 in the direction L1 at the end 50 a; and then lifting themicroplate 50 away from the holder 20. Alternatively, the microplate 50may be unloaded from the holder 20 by: flexing the end wall 24 outwardin the direction L2 and/or pushing the microplate 50 in the direction L1so as to flex the end wall 26 outward in the direction L1, such that theflange 57 is moved longitudinally inside of the catch 32 in thedirection L1 at the end 50 a; lifting the end 50 a up in the directionD2 such that the flange 57 moves up past the catch 32 at the end 50 a;sliding the microplate 50 backwards in the direction L2 such that theflange 57 is moved past the catches 34 in the direction L2 at the end 50b; and then lifting the microplate 50 away from the holder 20.

FIGS. 7-12 illustrate a magnetic microplate assembly 100 according toanother embodiment. Referring to FIGS. 7-11, the assembly 100 includes amagnetic microplate holder 120 and a microplate 50 retained in theholder 120.

Turning to FIGS. 9 and 10, the microplate holder 120 includes a bottomwall 122, a first end wall 124 formed at a first end of the bottom wall122, and a second end wall 126 formed at a second end of the bottom wall122, and side walls 128. The holder 120 is may be constructed ofnon-magnetic plastic, however, other materials may be used. A pluralityof cylindrical magnets 30 are positioned in the bottom wall 122, witheach magnet 30 being positioned for alignment directly below a well 58of the microplate 50. As in the previous embodiment, it should beunderstood that various numbers and arrangements of magnets arepossible.

Still referencing FIGS. 9 and 10, the end walls 124, 126 each include apair of recesses 133 at the corners 130, 131 where the end walls 124,126 join the side walls 128. The recesses 133 facilitate gripping of themicroplate 50 during loading and unloading of the microplate 50. Theside walls 128 include open sections 132 which allow a user to grab sideportions of the microplate 50 and also serve to prevent liquidaccumulation in the assembly 100 during washing of the microplate 50.

As shown in FIGS. 7-12, a pair of resilient detents, or spring-and-ballplungers 134 are provided in the end wall 124. As illustrated in FIG.13, the spring-and-ball plungers 134/138 each include a ball member135/139 seated on a spring 136/140 which applies a biasing force B1/B2that biases the ball member 135/139 in an extended position so as toprotrude from the inner surface 124 a/126 a of the end wall 124/126. Theball member 135/139 and spring 136/140 are seated in a bore 150/160 inthe end wall 124/126. The bore 150/160 extends entirely through the endwall 124/126, and has a first, open end 152/162 at the inner surface 124a/126 a of the end wall 124/126 and a second end 154/164 an outersurface 124 b/126 b of the end wall 124/126. The second end 154/164 isclosed by a plug 156/166. The spring 136/140 is seated against the plug156/166. The diameter of the bore 150/160 is slightly larger than thediameter of the ball member 135/139 at the second end 154/164 and anintermediate section 155/165. The diameter of the bore 150/160 isslightly smaller than the diameter of the ball 135/139 at the first end152/162, thereby allowing the ball member 135/139 to partially protrudefrom the first pen end 152/162 while being retained in the bore 150/160.Spring-and-ball plungers 134/138 can be installed in the end walls124/126 by inserting the ball member 135/139 and the spring 136/140through the second end 154/164 into the bore 150/160, and then securingthe plug 156/166 in the second end 156/166.

According to an alternate embodiment shown in FIG. 14, the ball member135/139 and spring 136/140 are seated in a bore 170/180 in the end wall124/126. The bore 170/180 extends partially through the end wall124/126, and has an open end 172/182 at the inner surface 124 a/126 a ofthe end wall 124/126 and a closed end 174/184 against which the spring136/140 rests at an interior portion of the end wall 124/126. The bore170/180 has a diameter that is slightly larger than the diameter of theball member 135/139. An annular reducer 176/186 having an inner diameterthat is slightly smaller than the diameter of the ball member 135/139 ispositioned at the open end 172/182, thereby allowing the ball member135/139 to partially protrude from the open end 172/182 while beingretained in the bore 170/180 by the reducer 176/186. According to thisembodiment, spring-and-ball plungers 134/138 can be installed in the endwall 124/126 by inserting the ball member 135/139 and the spring 136/140through the open end 172/182 into the bore 170/180, and then securingthe annular reducer 176/186 at the open end 172/182.

Referencing FIGS. 9-12, a detent or dowel pin 142 is attached to eachside wall 128 near the corners 130. The dowel pins 142 extend inwardlyfrom inside surfaces 128 a of the side walls 128 substantially parallelto the end wall 124. The spring-and-ball plungers 134, 138 and dowelpins 142 may be located at a height above the bottom wall 122 thatallows the bottom flange 57 of the microplate 50 to be tightly securedbelow the spring-and-ball plungers 134, 138 and dowel pins 142, as willbe described in greater detail in following paragraphs. As will bedescribed later, the spring-and-ball plungers 134, 138 and dowel pins142 cooperate to retain the microplate 50 in the holder 120. Although apair of spring-and-ball plungers 134, 138 are shown positioned incentral regions of the end walls 124, 126, and a pair of dowel pins 142are shown near the corners 130, it should be understood that otherarrangements and numbers of spring-and-ball plungers 134, 138 and/ordowel pins 142 are possible. In an alternate embodiment, the dowel pins142 may be replaced by other elongate catch members, or by catches orrib members positioned on the end wall 124.

FIGS. 7, 8 and 11 show the microplate assembly 100 in a fully assembledconfiguration. In this configuration, the microplate 50 is secured inthe holder 120 such that the bottom flange 57 is retained under thedowel pins 142 and the spring-and-ball plungers 134, 138. Specifically,the ledge 56 engages and is positioned below the dowel pins 142 at theend 50 a, and the ledge 56 engages and is positioned below thespring-and-ball plungers 134, 138 at the ends 50 a, 50 b, therebypreventing vertical movement of the microplate 50 during use. Theassembly 100 may be used to separate biological activated magneticparticles from a supernatant in the same manner as the assembly 10 ofthe previous embodiment. Supernatant and wash buffer may be discarded ina manner similar to that for discarding supernatant and wash buffer fromthe assembly 10, that is, by tilting or inverting the assembly 100 suchthat the upper platform 52 of the microplate 50 is turned downward. Theopen sections 133 of the side walls 128 assist in draining supernatantand wash buffer from the microplate 50. Due to the spring-and-ballplungers 134 and the dowel pins preventing vertical movement of themicroplate 50 within the holder 20, the microplate 50 is securelyretained close to the magnets 30 within the holder 120 during inversionor tilting of the assembly 100, thereby allowing the particles to remainwithin the wells 58.

FIG. 12 illustrates how the microplate 50 can be loaded into the holder120. As shown in FIG. 12, the microplate 50 can be loaded into theholder 120 by: tilting the end 50 b of the microplate 50 slightlydownward in the direction D1; sliding the microplate 50 longitudinallyforward in the direction L1 such that the end 50 b engages andcompresses the spring-and-ball plungers 138 towards the end wall 126,the ledge 56 moves below and into engagement with undersides of thespring-and-ball plungers 138, and the flange 57 moves longitudinallyinside of the dowel pins 142 and the spring-and-ball plungers 134 at theend 50 a of the microplate 50; pressing the end 50 a down in thedirection D1 such that flange 57 travels downward past thespring-and-ball plungers 134 and the dowel pins 142 at the end 50 a; andthen releasing the microplate 50 such that the spring-and-ball plungers138 return to their extended positions and force the microplate 50 tomove in the direction L2 such that the ledge 56 moves under and intoengagement with the undersides of the spring-and-ball plungers 134 andthe dowel pins 142 at the end 50 a.

Alternatively, the microplate 50 can be loaded into the holder 120 byfirst inserting the end 50 a. Specifically, the microplate 50 can beloaded into the holder 120 by: tilting the end 50 a of the microplate 50slightly downward in the direction D1; sliding the microplate 50longitudinally forward in the direction L2 such that the end 50 aengages and compresses the spring-and-ball plungers 134 towards the endwall 124, the ledge 56 moves below and into engagement with undersidesof the spring-and-ball plungers 134 and the dowel pins 142, and theflange 57 moves longitudinally inside of the spring-and-ball plungers138 at the end 50 b of the microplate 50; pressing the end 50 b down inthe direction D1 such that flange 57 travels downward past thespring-and-ball plungers 138 at the end 50 b; and then releasing themicroplate 50 such that the spring-and-ball plungers 134 return to theirextended positions and force the microplate 50 to move in the directionL1 such that the ledge 56 moves under and into engagement with theundersides of the spring-and-ball plungers 138.

Still referring to FIG. 12, the microplate 50 can be unloaded from theholder 120 by: pressing the end 50 b forward in the direction L1 againstthe spring-and-ball plungers 138 to compress the spring-and-ballplungers 138 towards the wall 126 and cause the flange 57 to move insideof the dowel pins 142 and the spring-and-ball plungers 134 at the end 50a; lifting the end 50 a upward in the direction D2 such that the flange57 moves up past the dowel pins 142 and the spring-and-ball plungers 134at the end 50 a; sliding the microplate 50 backwards in the direction L2such that the flange 57 is moved inside of the spring-and-ball plungers138 at the end 50 b; and then lifting the microplate 50 away from theholder 120. Alternatively, the microplate 50 can be unloaded from theholder 120 by: pressing the end 50 a backward in the direction L2against the spring-and-ball plungers 134 to compress the spring-and-ballplungers 134 towards the wall 124 and cause the flange 57 to move insideof the spring-and-ball plungers 138 at the end 50 b; lifting the end 50b upward in the direction D2 such that the flange 57 moves up past thespring-and-ball plungers 138 at the end 50 b; sliding the microplate 50forward in the direction L1 such that the flange 57 is moved inside ofthe spring-and-ball plungers 138 and the dowel pins 142 at the end 50 a;and then lifting the microplate 50 away from the holder 120.

In FIG. 15, an exploded view of the microplate holder 20 provides anexample of its construction. The upper portion of the plate holder 191contains each of the individual magnets 30. A bottom plate 192 attachesto the top section of the plate holder 191 and is held by pins 194. Pins194 may be constructed of plastic, metal or any material suitable forsecuring the plates sections 191 and 192. Pins may be any fasteninghardware suitable for attaching bottom plate 192 with plate holder topsection 191. Between these plate sections 191 and 192 is a metallicplate 193 which holds magnets 30 to the upper plate section 191 throughmagnetic force. Although magnets 30 may be secured to 191 by adhesive,friction or other suitable means, the metallic plate 193 is sufficientto keep 30 in place. Similarly, the metallic plate 30 is held in placeby the magnets but also may be attached to either 191, 192 or both bythe use of an adhesive, friction or other suitable means. The plate 193may be made from any ferromagnetic material, or may be itself magnetic.Plate 193 may be excluded from microplates where magnets 30 are securedto the top plate section 191 by adhesive, friction or other suitablemeans, although plate 193 may still be included in the assembly toprovide further securing of the magnets 30.

The foregoing disclosure provides illustrative embodiments of theinvention and is not intended to be limiting. It should be understoodthat modifications of the disclosed embodiment are possible within thespirit and scope of the invention, and the invention should be construedto encompass such modifications.

What is claimed is:
 1. A microplate assembly for assaying biologicalmaterial, comprising: a microplate comprising: wells for holdingbiological particles, an upper platform, the wells being located in theupper platform, a perimeter wall extending downward from the upperplatform and including an upper wall portion and a stepped-out bottomflange; and a microplate holder for retaining the microplate, themicroplate holder comprising: a bottom wall comprising at least onemagnet, a first end wall located at a first end of the bottom wall, asecond end wall located at a second end of the bottom wall, at least onefirst detent comprising a catch located on an inner surface of the firstend wall, substantially open side portions extending between the firstend wall and the second end wall, and at least one second detentcomprising a second catch located on an inner surface of the second endwall, wherein the catch of the at least one first detent and the catchof the at least one second detent on the microplate holder are arrangedto engage the bottom flange on the microplate, thereby securing themicroplate in the microplate holder, wherein the first end wall or thesecond end wall on the microplate holder comprises a cut-out portionsuitable for gripping the microplate, wherein the bottom wall furthercomprises: a third end of the bottom wall between the first end of thebottom wall and the second end of the bottom wall; and a fourth end ofthe bottom wall, opposite the third end, and arranged between the firstend of the bottom wall and the second end of the bottom wall, andwherein one of the open side portions extends as a single open sideportion across substantially the entire third end of the bottom wall andanother open side portion extends as a single open side portion acrosssubstantially the entire fourth end of the bottom wall.
 2. Themicroplate assembly of claim 1, wherein the at least one first detentand the at least one second detent are arranged to engage asubstantially horizontal surface of the microplate.
 3. The microplateassembly of claim 1, wherein the bottom flange includes a horizontalledge joined to the upper wall portion, and wherein the at least onefirst detent and the at least one second detent are arranged to engagethe horizontal ledge.
 4. The microplate assembly of claim 1, wherein thefirst end wall and the second end wall are flexible and resilient, so asto allow end portions of the microplate to be inserted under and removedfrom under the at least one first detent and the at least one seconddetent.
 5. The microplate assembly of claim 1, wherein the catch of theat least one first detent and the catch of the at least one seconddetent on the microplate holder prevent vertical movement of themicroplate during use.
 6. The microplate assembly of claim 1, whereinthe catch of the at least one first detent and the catch of the at leastone second detent on the microplate holder retain the microplate withinthe microplate holder during inversion or tilting of the microplateassembly.
 7. The microplate assembly of claim 1, wherein the cut-outportion extends from an upper edge of the first end wall or the secondend wall towards a lower edge of the first end wall or the second endwall, and wherein a height of the first end wall or the second end wallat the cut-out portion is less than a height of the first end wall orthe second end wall surrounding the cut-out portion.
 8. A microplateholder suitable for holding a microplate for assaying biologicalmaterial, the microplate holder comprising: a bottom wall comprising atleast one magnet, a first end wall located at a first end of the bottomwall, a second end wall located at a second end of the bottom wall, atleast one first detent comprising a catch located on an inner surface ofthe first end wall, substantially open side portions extending betweenthe first end wall and the second end wall, and at least one seconddetent comprising a second catch located on an inner surface of thesecond end wall, wherein the microplate comprises: an upper platform;and a perimeter wall extending downward from the upper platform andincluding an upper wall portion and a stepped-out bottom flange, whereinthe catch of the at least one first detent and the catch of the at leastone second detent on the microplate holder are arranged to engage thebottom flange on the microplate thereby securing the microplate in themicroplate holder, wherein the first end wall or the second end wall onthe microplate holder comprises a cut-out portion suitable for grippingthe microplate, wherein the bottom wall further comprises: a third endof the bottom wall between the first end of the bottom wall and thesecond end of the bottom wall; and a fourth end of the bottom wall,opposite the third end, and arranged between the first end of the bottomwall and the second end of the bottom wall, and wherein one of the openside portions extends as a single open side portion across substantiallythe entire third end of the bottom wall and another open side portionextends as a single open side portion across substantially the entirefourth end of the bottom wall.
 9. The microplate holder of claim 8,wherein the at least one first detent and the at least one second detentare arranged to engage a substantially horizontal surface of themicroplate.
 10. The microplate holder of claim 8, wherein the microplateholder is suitable for holding a microplate wherein the bottom flange ofthe microplate includes a horizontal ledge joined to the upper wallportion, and wherein the at least one first detent and the at least onesecond detent of the microplate holder are arranged to engage thehorizontal ledge of the microplate.
 11. The microplate holder of claim8, wherein the first end wall and the second end wall are flexible andresilient, so as to allow end portions of the microplate to be insertedunder and removed from under the at least one first detent and the atleast one second detent.
 12. A microplate holder suitable for holding amicroplate comprising wells for holding a test sample, the microplateholder comprising magnets for magnetic separation of material in thetest sample containing or bound to ferromagnetic or paramagneticmaterial and wherein the ferromagnetic or paramagnetic material remainswithin the wells of the microplate by magnets attached to the microplateholder by magnetic attraction to the microplate, and wherein themicroplate holder further comprises: a bottom wall, a first end walllocated at a first end of the bottom wall, a second end wall located ata second end of the bottom wall, at least one first detent comprising acatch located on an inner surface of the first end wall, substantiallyopen side portions extending between the first end wall and the secondend wall, and at least one second detent comprising a second catchlocated on an inner surface of the second end wall, wherein the firstend wall or the second end wall on the microplate holder comprises acut-out portion suitable for gripping the microplate, wherein the bottomwall further comprises: a third end of the bottom wall between the firstend of the bottom wall and the second end of the bottom wall; and afourth end of the bottom wall, opposite the third end, and arrangedbetween the first end of the bottom wall and the second end of thebottom wall, and wherein one of the open side portions extends as asingle open side portion across substantially the entire third end ofthe bottom wall and another open side portion extends as a single openside portion across substantially the entire fourth end of the bottomwall.
 13. The microplate holder of claim 12, wherein the at least onefirst detent and the at least second detent are securing means forattaching a microplate to the microplate holder, said securing meansallowing inversion of the microplate holder and attached microplate suchthat the contents of the microplate may be emptied.
 14. A microplateassembly for assaying biological material, comprising: a microplatecomprising: wells for holding biological particles, an upper platform,the wells being located in the upper platform, a perimeter wallextending downward from the upper platform and including an upper wallportion and a stepped-out bottom flange; and a microplate holder forretaining the microplate, the microplate holder comprising: a bottomwall, a first end wall located at a first end of the bottom wall, asecond end wall located at a second end of the bottom wall, at least onefirst catch located on an inner surface of the first end wall at leastone second catch located on an inner surface of the second end wall,substantially open side portions extending between the first end walland the second end wall, and at least one magnet positioned on thebottom wall, wherein the first catch and the second catch on themicroplate holder are arranged to engage the bottom flange on themicroplate, thereby securing the microplate in the microplate holder;wherein the magnet on the microplate holder is suitable for retainingmagnetic particles in the wells on the microplate, wherein the bottomwall further comprises: a third end of the bottom wall between the firstend of the bottom wall and the second end of the bottom wall; and afourth end of the bottom wall, opposite the third end, and arrangedbetween the first end of the bottom wall and the second end of thebottom wall, and wherein one of the open side portions extends as asingle open side portion across substantially the entire third end ofthe bottom wall and another open side portion extends as a single openside portion across substantially the entire fourth end of the bottomwall.
 15. The microplate assembly of claim 14, wherein the microplateholder comprises at least one circular magnet.
 16. The microplateassembly of claim 14, wherein the magnet on the microplate holder iscircular.
 17. The microplate assembly of claim 14, wherein the numberand arrangement of magnets on the microplate holder are the same as thenumber and arrangement of the wells on the microplate.
 18. Themicroplate assembly of claim 14, wherein the first and second catchesare arranged to engage a substantially horizontal surface of themicroplate.
 19. The microplate assembly of claim 14, wherein the bottomflange on the microplate includes a horizontal ledge joined to the upperwall portion, wherein the first and second catches on the microplateholder are arranged to engage the horizontal ledge on the microplate,and wherein the microplate is inserted under and removed from under thefirst and second catches on the microplate holder.
 20. The microplateassembly of claim 14, wherein at least one of the first end wall and thesecond end wall of the microplate holder comprises a cut-out portionsuitable for gripping.
 21. The microplate assembly of claim 14, whereinthe first and second catches on the microplate holder prevent verticalmovement of the microplate during use.
 22. The microplate assembly ofclaim 14, wherein the first and second catches on the microplate holderretain the microplate within the microplate holder during inversion ortilting of the microplate assembly.
 23. The microplate assembly of claim14, wherein the wells on the microplate comprise magnetic particles. 24.The microplate assembly of claim 23, wherein the magnetic particles areretained in the wells on the microplate by the circular magnets on themicroplate holder during inversion or tilting of the microplateassembly.
 25. The microplate assembly of claim 14, wherein themicroplate comprises ninety-six (96) wells and the microplate holdercomprises ninety-six (96) circular magnets.